The first totalsynthesis of the novel glycosylated tetrahydroisoquinoline antitumor antibiotic (-)-lemonomycin has been accomplished (15 steps from 9). The highly convergent synthesis relies on a key asymmetric dipolar cycloaddition to set the stereochemistry of the aglycone core, a Suzuki fragment coupling to connect the diazabicycle to the aryl subunit, and a stereoselective Pictet-Spengler reaction